Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$127.51	13.363%	$144.5492	$144.55	$144.55	$144.50
Purchase #2	$113.50	3.482%	$117.4521	$117.45	$117.45	$117.50
Purchase #3	$37.44	3.546%	$38.7676	$38.77	$38.75	$38.80
Purchase #4	$216.94	12.583%	$244.2376	$244.24	$244.25	$244.20
Purchase #5	$175.34	13.706%	$199.3721	$199.37	$199.35	$199.40
Purchase #6	$169.38	8.453%	$183.6977	$183.70	$183.70	$183.70
Purchase #7	$119.90	6.149%	$127.2727	$127.27	$127.25	$127.30
7 purchase totals =	$960.01		$1,055.3490	$1,055.35	$1,055.30	$1,055.40